Variation Of Arc Length Research Articles

Influence Mechanism of Kinematic Properties on Drastic Arc Length Variation during Secondary Arc Motion near Power Transmission Line Insulator String

Influence Mechanism of Kinematic Properties on Drastic Arc Length Variation during Secondary Arc Motion near Power Transmission Line Insulator String

Study on the Modeling and Suppression of Arcing Generated by Articulated Split-Zone Insulator in Electrified Railways

In electrified railways, pantograph–catenary (PC) arc frequently occurs in the process of train passing through split-zone insulator, which threatens the current collection of PC and operation of electric multiple units (EMUs). So far, there have been a few studies on the analysis and modeling of the PC arc on split-zone insulator. It is noting that this research is different from that of split-phase region. This article first analyzes the dynamic variation process of PC distance as EMUs pass the insulator and deduces the formula, which can reflect the PC arc length variation according to the specific mechanical structure of insulator. Then, a black-box arc model of split-zone insulator is proposed. Next, a vehicle-to-grid model of the EMUs that contains the arc model of split-zone insulator is established to simulate and analyze the characteristics of the PC arc on split-zone insulator. Furthermore, the proposed arc model in this article is verified by comparing the simulated arc characteristic waveforms with the measured results. Finally, a sensitivity analysis of the arc model under different lifting angles of the contact wire is carried out in order to analyze the suppression of PC arc on split-zone insulator.

Shape optimization of generalized developable H-Bézier surfaces using adaptive cuckoo search algorithm

The shape optimization design of developable surface is a critical and intractable technique in CAD/CAM and used in many manufacturing planning operations. In this paper, we study shape optimization by using a new cuckoo search (CS) algorithm to promote the development of generalized developable H-Bézier surfaces (or GDHBS, for short). According to the duality between points and planes in 3D projective space, the GDHBS shape optimization problem is formulated as an arc length, energy and curvature variation minimization problem of dual curve, respectively. Then, an adaptive CS optimization algorithm is applied to the solutions of those GDHBS shape optimization models. Finally, we illustrate the effectiveness and performance of the proposed methods by some representative and convictive examples.

Hot-wire arc additive manufacturing Ti–6.5Al–2Zr–1Mo–1V titanium alloy: Pore characterization, microstructural evolution, and mechanical properties

Hot-Wire Arc Additive Manufacturing (HWAAM) is a promising process to fabricate large-scale integral components. Systematic researches are necessary to establish the initial material-processing-microstructure-property relationships in HWAAM. In this study, two TA15 titanium alloy block parts were built by HWAAM with two batches of wire. Notches on the wire surface and wire warpage aggravated the porosity of the built part. Quantitative characterization and analysis of pores were performed by X-ray computed tomography. Most of the pores were clustered at the fusion boundary. The porosity of the bead body zone was higher than that of the bead overlap zone. The equivalent diameters of pores primarily concentrated in a narrow range of variation. Spherical trapped gas pores were induced by hydrogen rejection. Irregularly shaped lack of fusion pores were caused by arc length variation, wire warpage and excessive heat input. The formation of equiaxed β grains were promoted by high porosity and low temperature gradient in the bead body zone. The poor ductility of the part with high porosity was attributed to the presence of pores and grain boundary α, while relatively high tensile strength of the part was attributed to the solid solution strengthening and boundary strengthening.

On logarithmic improvements of critical geodesic restriction bounds in the presence of nonpositive curvature

We consider upper bounds on the growth of L p norms of restrictions of eigenfunctions and spectral clusters to geodesic segments in a nonpositively curved manifold in the high frequency limit. This sharpens results of Chen and Sogge as well as Xi and Zhang, which showed that the crux of the problem is to establish bounds on the mixed partials of the distance function on the covering manifold restricted to geodesic segments. The innovation in this work is the development of a formula for the third variation of arc length on the covering manifold, which allows for a coordinate free expressions of these mixed partials.

Research on arc interference and welding operating point change of twin wire MIG welding

In order to improve the understanding on arc interference behavior and verify the welding operating point change during twin wire MIG welding, the synchronous acquisition system has been established to acquire instantaneous information of electric signals, arc profile, and droplet transfer including dynamic arc length variation. It showed that the current and voltage signals changed significantly after trailing arc (T-arc) was added to the leading arc (L-arc) in a stable welding process. Moreover, the arc agitation of L-arc increased with increasing the current of T-arc but decreased with increasing the inter-wire distance. The results also showed that the stable spray transfer of L-arc was destroyed and deflected due to the effect of T-arc. With respect to a single wire welding, the arc length of L-arc increased and the welding operating point changed during the twin wire welding.

Analysis of arc interference and welding stability in twin wire GMA welding

In order to better understand the arc interference behavior and welding stability in twin wire GMA welding, the synchronous acquisition system has been established to acquire instantaneous information of electric signals, arc profile, and droplet transfer including dynamic arc length variation. The results showed that after Trailing arc (T-arc) was added to the Leading arc (L-arc) in a stable welding process, the current of L-arc decreased and the voltage kept constant. The stable globular transfer of L-arc was destroyed and deflected, turned into spray transfer due to the effect of T-arc. Compared to the single wire welding, the arc length of L-arc increased and the welding operating point changed in twin wire welding.

Rough set based modeling for welding groove bottom state in narrow gap MAG welding

Purpose – This paper aim to build an information fusion model that can predict the bottom shape of welding groove for better welding quality control. Arc sensor is widely used in seam tracking due to its simplicity and good accessibility, but it heavily relies on the bottom shape of the groove. It is necessary to identify the welding groove bottom state. Therefore, arc sensor information and vision sensing information were fused by the rough set (RS) method to predict the groove state, which will lay the foundation for better welding quality control. Design/methodology/approach – First, a multi-sensor information system was established, which included an arc sensing component and a vision sensing component. For the arc sensing system, the current waveform in each rotating period was obtained and divided into 12 parts to calculate variables representing the variation of arc length. For the vision sensing system, images were obtained by passive vision when the arc was near the groove sidewall. The positions of the sidewall and the arc were calculated to get the weld deviation which was unrelated with the bottom groove state. Second, experimental data were generated by workpiece with various bottom shapes. At last, the RS method was adopted to fuse the arc sensing and the vision information, and a rule-based model with good prediction ability was obtained. Findings – By fusing arc sensing and vision sensing information, an RS-based model was built to predict the welding groove state. Originality/value – The RS modeling method was used to fuse arc sensing information and vision sensing information to build a model that predicts groove bottom state. The arc sensing information represented the arc length variation, while the vision sensing information contains the seam deviation which was unrelated with the bottom groove state. The RS model gives satisfactory prediction results and can be applied to weld quality control.

Real-time control of welding penetration during robotic GTAW dynamical process by audio sensing of arc length

This paper presents a new technology of real-time arc length monitoring and sag-depression prediction through arc sound signal, which is essential to realize the welding penetration control during gas tungsten arc welding of arc length. A set of automatic measurement and control system have been proposed to achieve real-time arc length control via audio sensing system. After preprocessing of arc sound signal, the piecewise linear models of arc sound signal were established under two different arc length variation 3–4 and 4–5–6 mm, analyzing the prediction errors of linear model, which were proved to be good enough for online monitoring of arc length in pulse GTAW. Based on the linear relationship between arc sound and arc length, the linear fitting model was implemented on predicting the surface height of weld pool. A segmented self-adaptive PID controller was proposed to achieve the monitoring and controlling of arc length;, the confirmatory experiments have been designed to test the control effect of arc-length monitoring based on arc sound signal.

Arc Interference Behavior during Twin Wire Gas Metal Arc Welding Process

In order to study arc interference behavior during twin wire gas metal arc welding process, the synchronous acquisition system has been established to acquire instantaneous information of arc profile including dynamic arc length variation as well as relative voltage and current signals. The results show that after trailing arc (T-arc) is added to the middle arc (M-arc) in a stable welding process, the current of M arc remains unchanged while the agitation increases; the voltage of M arc has an obvious increase; the shape of M arc changes, with increasing width, length, and area; the transfer frequency of M arc droplet increases and the droplet itself becomes smaller. The wire extension length of twin arc turns out to be shorter than that of single arc welding.

An Automatic Control System Based on Arc Voltage of TIG Welding

This paper describes an automation welding control system for Tungsten inert gas shielded (TIG) welding to maintain constant arc length. And using this method can replace manual operation. A voltage transducer was used to avoid high-frequency voltage. And dynamic relation between variation of arc length and voltage are described. A digital Proportion-Integration-Differentiation (PID) controller with identified value has been used modulate the rate of electrode feed mechanism. The mechanism, which driven by Servomotor A, can compensated variation of arc length in welding path. By keeping the arc length constant during the welding process, an elegant appearance and higher quality seam is obtained. The experiment result shows that this automatic control system based on digital PID controller is stable, and can working effectively without operator manipulation.

Energy Fluctuations in a Direct Current Plasma Torch with Inter-Electrode Inserts Operated at Reduced Pressure

Direct current (dc) plasma torch with inter-electrode inserts has the merits of fixed arc length, relative high enthalpy and may show advantages in future plasma processes where stability and controllability are must-have. Energy fluctuations in the plasma may result from power supply ripple, arc length variation, and/or acoustic oscillation. Using an improved power supply with a flat waveform, the characteristics of an argon plasma energy instabilities under reduced pressure were studied by means of simultaneously monitoring the arc voltage and arc current spectrum. Dependence of the arc fluctuation behavior on the plasma generating parameters, such as the current intensity, the plasma gas flow rates and the vacuum chamber pressure were investigated and discussed. Results show that the plasma torch has a typical U-shaped voltage-ampere characteristic (VAC). The correlation between the VAC and the probability of energy distributions was studied. Through pressure measurements at the cathode cavity and the vacuum chamber, the existence of sonic flow in the inter-electrode insert channel was confirmed.

A Numerical Model with arc length variation of welding arc with constant voltage power source

In the present paper, Tungsten Inert Gas (TIG) arc with Constant Voltage (CV) power source is modelled if arc length changes. And TIG arc with Constant Current (CC) power source is also modelled if arc length changes. The TIG arc is assumed on base material of water-cooled copper. For the CV power source, maximum temperature of arc plasma and arc current increase with decrease of arc length. For the CC power source, arc voltage changes but maximum temperature of arc plasma is almost constant in spite of change of arc length. Arc power increases with decrease of arc length for the CV power source. On the other hand, arc power decreases with decrease of arc length for the CC power source. For the CV power source, arc power changes largely if arc length changes. However, for the CC power source, arc power changes little if arc length changes. Heat input from welding power source is more stable using a CC power source than a CV power source at TIG welding with a change of arc length.

Visual evaluation of the length of artificially generated electrical discharges by 3D-snakes

The secondary arc extinction is the main concern in single-phase auto reclosure (SPAR) switching studies, since it dictates whether the reclosure will be successful or not. In this context, a function that describes the arc length variation over time (l(t)) is an important information not only for dynamic response but also for the analysis of transient arc processes. Given that purely electrotechnical approach only gives a profile of the curve l(t), the application of techniques based on image analysis has been considered for obtaining such function. In this paper, a new approach based on 3D-reconstruction and the tracking of an electrical arc is proposed for performing a computer-based evaluation of variations in its length. It was applied a three-dimensional active contour named 3D-snake that is geometrically represented by a B-spline, which evolves in 3D space. This new model is much less dependent on the determination of homologous points than the ad hoc approaches found in the literature for recovering 3D geometry of electrical discharges based on image analysis. In addition, the proposal presented is capable of tracking the evolution of the electrical discharge taking into account the time dependence between consecutive pairs of frames in two videos providing the required function l(t).

Deriving the ADM3+1evolution equations from the second variation of arclength

We will show that the ADM 3+1 evolution equations, for a zero shift vector, arise naturally from the equations for the second variation of arclength.Received 22 May 2009DOI:https://doi.org/10.1103/PhysRevD.80.084030©2009 American Physical Society

Mathematic model of high speed rotational arc sensor

A mathematical model of high speed rotational arc sensor, which is used in gas metal arc welding (GMAW) of fillet joints, is developed. It is based on the mathematical model of GMA welding system and Halmoy's wire melting model. The variations of welding current, arc length and wire extension are simulated by using the developed model. It is shown that the simulation results of welding current, arc length and wire extension agree with the experimental results in fillet joints. Based on the mathematical model, the variation of arc length is bigger than that of wire extension. The deviation and direction of the welding gun can be detected by the difference between the left half-cycle current and the right half-cycle current during each torch rotational cycle. In addition, the end point of the fillet joint can be detected by the average current value in each torch rotational cycle. The mathematical model developed is helpful to the design and application of high speed rotational arc sensors.

Long arc in free air elongation effects modeling and simulation

AbstractIn the paper the elongation effects on the long arc in still air are investigated and modelled. Arc is initiated under laboratory conditions in the high power test laboratory FGH‐Mannheim (Germany). Based on the analysis of laboratory arc voltage and current wave forms, the new dynamic arc model, taking into account the arc length variation, is derived. An example of arc computer simulation using the new model is given. The main features of the simulated arc are presented. The main features of both the real and the simulated arc are given in the time and the spectral domains.

New dynamic model, laboratory testing and features of long arc in free air

In this paper the long arc in free air is investigated. First, arc is initiated under laboratory conditions in the high power test laboratory FGH-Mannheim (Germany). Based on the laboratory obtained data records, the main features of arc are derived. By this arc, voltage and current are processed. An important feature of arc, the variation of arc length, is analyzed. Based on the analysis of arc voltage and current wave forms, the new dynamic arc model, taking into account the arc length variation, is derived. Arc is modeled as a current dependent voltage source with the characteristic distorted rectangular waveform and arc length dependent amplitude. Arc is considered as a source of higher harmonics distorting by this other signals in the network. An example of arc computer simulation using the new model is given. The main features of simulated arc are presented, too. Features of both the real and the simulated arc are given in the time and the spectral domains.

亜鉛めっき鋼板のアーク溶接における溶融池振動による気孔の低減

With respect to the blowholes to be formed by the vaporized zinc gas coming into a molten pool through the gap of seams in the consumable electrode type pulsed arc welding of galvanized carbon steel sheets, the means to decrease the number of them by inducing the flow of molten metal along the bottom face of the molten pool has been examined and studied. As the result of the vibration of mother metals by 1 mm while welding so as to produce the back and forth flow of molten metal at the bottom face by the longitudinal vibration of molten pool, the significant reduction of blowholes has been achieved. The optimum frequency of vibration seems to be about scores of frequency (Hz) which can be supposed to be the self vibration frequency to be determined depending on the size of molten pool, physical properties of type of molten metal, etc. In order to obtain the same effect as the above by the control of electric current, by minimizing the variation of arc length, the process to alternately repeat the pulse electric current wave groups of both high peak in a short time and low peak in a long time to periodically change arc force at the same time has been studied. It has been found that the molten pool can be vibrated in a longitudinal direction also by the control of arc force and it has also been found that the generation of blowholes can significantly be reduced by this vibration. The vibration of molten pool is effective for the promotion of removal of not only the blowholes to be caused by generation of zinc gas but also those of supersaturation type by the nitrogen to be formed on the metal surface in the progress of their solidification.

An unknotting result for complete minimal surfaces R3

In this note we prove: Theorem. If S is a complete properly embedded minimal surface in R 3, with the Euclidean metric, and if A is a closed connected complementary domain of Z, then either A is metrically R 2  [0, hi or, up to diffeomorphism, A is made from a countable or finite collection of building blocks by attaching a proper collection of closed 1-handles. Each building blocks is a closed 3-ball or an open annulus x [0, 1). [] The first theorem of this kind was B. Lawson's I-L] unknottedness theorem for minimal surfaces in S 3. That result was obtained by considering the second variation of arc length. Because the flat Euclidean metric of R 3 does not contribute a favorable curvature term as found in S 3 a dual approach employing stable minimal surfaces (dual to Lawson's spanning arcs) is required. The key technical result, proved by an analysis of the second variation operator on surfaces, is that geometric planes are the only stable minimal surfaces in R 3 [C, P] and [F-C, S]. From this starting point a more topological theory has been developed by Frohman, Hoffman, Meeks, Yau, and others. Our argument is based, to a large degree, on the methods used by C. Frohman and W. Meeks [F, M] to classify 1-ended, proper, complete, minimal, imbeddings in R 3. We present four succinct topological assertions about any 3-manifold with boundary (A, S) which is a connected, closed complementary region of a complete proper minimal surface in R 3. These statements should be thought of as "axioms" for this emerging theory. Deduced from geometry, they help to mark the boundary with topology. The theorem follows quickly from the axioms. Axiom 1 occurs explicitly as corollary 3.2 I-F, M]. Axiom 2 is an immediate consequence of the methods of [F, M] and Axiom 3 is proved by an extension of these methods. Axiom 4 is related to an idea on the ordering of ends [M, Y] due to W. Meeks and S.-T. Yau. These are the axioms. Their verification actually only requires that the mean curvature vector of 2: be everywhere zero or pointing towards A.